PROJECT SUMMARY Vasomotor symptoms (VMS), also known as hot flashes, are common perturbations of perceived high temperature that women experience during menopause as a consequence of the depletion of estradiol levels. These VMS entail profuse sweating and peripheral vasodilation that can adversely affect quality of life in menopausal women, relevant to subsequent risk of cardiovascular disease and dementia. Recently, neurons producing the neuropeptides kisspeptin (encoded by the Kiss1 gene), neurokinin B (NKB, encoded by Tac2), and dynorphin (Dyn, encoded by Pdyn) and referred to as KNDy neurons in the hypothalamic arcuate nucleus of mice have been identified as mediators of hot flashes through a common pathway that also controls pulsatile GnRH secretion and the activity of the hypothalamic-pituitary-gonadal (HPG) axis. Based on this dual role of KNDy neurons, we hypothesize that factors that negatively impact reproductive function, such as stress and hypercortisolemia, act through KNDy neurons and will also affect thermoregulation (i.e., VMS) and sleep in menopausal patients. To this end, using mouse models of menopause and VMS, we aim to: 1) determine if these effects occur through direct regulation of Kiss1 or indirectly through regulation of Tac2 or Pdyn; and 2) determine if these effects occur on the KNDy neurons themselves and/or via neurons upstream of KNDy neurons?specifically, via GABAergic neurons. In addition, given the association of the menopausal decline of sex steroids with not only VMS but also disruption of sleep patterns, we aim to explore the relationships of stress, corticosteroids and KNDy neurons in the absence of sex steroids with sleep disruption. The successful completion of this proposal will offer important new mechanistic insights into the roles and effects of stress on KNDy neurons, the HPG axis, VMS, and associated sleep disturbances with the assistance of the Sleep Core. These insights will be critical to inform the development of new, safer and more effective tools to mitigate the effects of stress and of hot flashes in women, as studied in Project 1 and Project 2 of this SCORE application, and thereby improve reproductive health aging outcomes in women.